1. Technical Field
The present invention relates to a liquid ejecting head and a liquid ejecting apparatus using the same.
2. Related Art
A typical example of liquid ejecting heads is an ink jet recording head including a vibrating plate which constitutes a portion of a pressure-generating chamber communicated with a nozzle orifice which ejects ink droplets so that the vibrating plate is deformed by a piezoelectric element to apply pressure to ink in the pressure-generating chamber, ejecting the ink as ink droplets from the nozzle orifice. An example of the piezoelectric element used in the ink jet recording head includes a piezoelectric layer composed of a piezoelectric material exhibiting an electro-mechanical conversion function, for example, a crystallized dielectric material, the piezoelectric layer being interposed between two electrodes. Such a piezoelectric element is mounted as a flexural oscillation-mode actuator device on a liquid ejecting head. The piezoelectric element mounted on the ink jet recording head is formed by, for example, forming a uniform piezoelectric material layer over the whole surface of the vibrating plate by a film forming technique and cutting the piezoelectric material layer into a shape corresponding to a pressure-generating chamber by lithography so that the piezoelectric material layer is independent for each pressure-generating chamber.
The piezoelectric material used for such a piezoelectric element is required to have high displacement characteristics and a high Curie temperature. A typical example of piezoelectric materials satisfying these conditions is lead zirconate titanate (PZT) (refer to, for example, Japanese Unexamined Patent Application Publication No. 2001-223404).
However, a piezoelectric material not containing lead which is a harmful substance is required from the viewpoint of environmental pollution. An example of the piezoelectric material not containing lead is BiFeO3 having a perovskite structure represented by ABO3. BiFeO3 is a material having excellent piezoelectric characteristics and has the advantage of a high Curie temperature due to covalent bonds formed between bismuth and oxygen and between iron and oxygen
On the other hand, a piezoelectric element using BiFeO3 as a piezoelectric material has a leakage current and has the problem that dielectric breakdown may occur even at a driving voltage of, for example, about 25 V. In addition, a piezoelectric element using BiFeO3 as a piezoelectric material has a high offset voltage (critical voltage), i.e., a high lower limit of operating voltage, and thus has the problem of the need to apply a high bias voltage. These problems are not limited to liquid ejecting heads such as the ink jet recording head, but are also present in liquid ejecting heads mounted on other apparatuses.